//author:dhclly
const o =console.log;
//要求 person 的type 是string
function greeter(person:string) {
    return "Hello, " + person;
}

let user = "Jane User";
o(greeter(user))

//error TS2345: Argument of type 'string[]' is not assignable to parameter of type 'string'.
let user2 = ["Jane User ","Tim Ted"];
o(greeter(user2))